Fluorescent lighting fixtures are now in use for providing illumination of large rooms, such as those found in offices and stores, as well as narrow areas such as hallways and stairways. These lighting fixtures can be operated at greatly reduced costs when compared to incandescent light fixtures. Also, fluorescent tubes provide even distribution of light without glare.
However, shortcomings exist in fluorescent lighting fixtures now being used, mainly related to their inefficient use of the available light. These fixtures usually employ translucent covers beneath the fluorescent tubes to diffuse the light evenly over the area of illumination; these translucent covers absorb light, thereby hampering efficiency.
A further deficiency is related to the housings in which the fluorescent tubes or bulbs are mounted for illumination. The housings absorb light directed from the bulb toward the back and sides of the housings. In addition, the geometry of the housings causes light interference patterns which further limits the total amount of light reflected out of the fixture. Quite often the housings are flat and rectangular, with the interior surfaces painted white to facilitate reflection of light outward. A significant amount of light produced by bulbs in multi-bulb housings travels either directly from one bulb to another or indirectly from one bulb to another by being reflected from an interior surface of the housing into another bulb.
The foregoing approaches waste energy. A significant portion of light produced by the tubes is attenuated within the housing, so less light is available to illuminate the area of interest.
Various attempts have been made to alleviate the foregoing problems. Partial solutions are offered by the following U.S. Pat. Nos. 2,194,841; 2,341.658; 2,864,939; 2,914,657; 3,829,677; 4,174,533; 4,242,725; 4,336,576; and 4,388,675.
U.S. Pat. No. 2,194,841 to Welch shows the mounting of a V-shaped reflector behind a fluorescent tube. The surfaces of the reflector direct light from the tube to other reflecting surfaces and then out of the fixture housing. Because of the multiple reflection the light undergoes, light efficiency suffers.
U.S. Pat. No. 2,341.658 to Salani discloses a light reflecting apparatus for focusing light from an intense single light source. The multiple flat reflecting surfaces are intentionally designed to cause the light rays to cross. The overall effect of the flat reflecting surfaces is to provide a reflector having a parabolic longitudinal curvature.
U.S. Pat. No. 2,864,939 to Bodian et al. discloses a shallow luminescent fluorescent light fixture. V-shaped reflectors are placed with their apex behind the fluorescent tubes to reflect light which would usually be lost in a flat fixture without V reflectors. Unfortunately, a significant portion of the light is reflected back into the bulbs, to thereby increase light interference and reabsorption and heat the tubes undesirably.
U.S. Pat. No. 2,914,657 to Akely et al. provides outdoor lighting fixtures suitable for use over areas such as gas filling station pump islands. In this case, V-shaped reflectors are aligned longitudinally in the fixtures so the apex of each V is midway between adjoining fluorescent tubes. Once again, a drawback is that a portion of the light is reflectd back into the tubes, thereby creating inefficiences.
U.S. Pat. No. 3,829,677 to DeLlano offers a reflecting means used in connection with fluorescent tubes. In this case, a parabolic reflector positioned behind the fluorescent tube is provided with a raised, inverted and smaller parabolic reflector located directly behind the tube. The reflectors are formed of rigid metallic materials which are not adjustable and are heavy to handle and be supported by the light fixture.
U.S. Pat. No. 4,174,533 to Barthes et al. discloses a wave flux concentration reflector in which a first trough-shaped reflector and a second reflector consists of two parabolic portions. The structures are so arranged that the aperture of the emergent beam is controllable. This arrangement is relatively complex and costly.
U.S. Pat. No. 4,242,725 to Douma et al. provides a parabolic reflector in which can be positioned an inverted V reflector with its apex behind an elongated intense light source. The shape of this reflector is determined at the point of manufacture; it is not adjustable in the field for retrofitting. Further, its construction is more complex than the construction of reflectors having flat surfaces.
U.S. Pat. No. 4,336,576 to Crabtree provides a lighting aparatus having less than the conventional number of light sources. The curved surfaces of the light reflector are constructed to reflect a ghost image of a tube into another portion of the light fixture, to thereby create the illusion to a viewer of multiple light sources. It is intended that this will have the psychological effect of convincing a light user there are more light sources than there actually are, to thereby reduce the number of light sources necessary in the fixture. The reflecting surfaces are intentionally designed to cause light rays to converge and cross, thereby creating the ghost tube image. The intended interference patterns, then, are used to advantage.
U.S. Pat. No. 4,388,675 to Lewin provides a lighting fixture having a plurality of inverted V-channels positioned behind fluorescent tubes in a light fixture. One set of channels is located with the apex directly behind a tube. Another set of channels has its members positioned midway between each light tube. All reflecting surfaces are covered with a specular material. The reflectors are permanently affixed to a fixture housing at the point of manufacture.
While the above patents do offer laudable approaches and solutions with respect to the particular situation each addresses, none of them individually or in combination disclose or suggest the invention defined by the appended Claims of this present case. Specifically, the following problems have not been adequately solved by the existing art. Existing light fixtures already mounted in, for example, office buildings and hallways do not lend themselves to easy retrofitting with presently used reflectors. Either the fixtures have built-in reflector surfaces with geometries making retrofitting with existing insert reflectors difficult or impractical, or the reflectors used for retrofitting are costly, cumbersome, limited for use in a particular fixture for which each reflector was designed, and heavy because the typical construction provides a specular metal reflecting surface overlying a base formed from steel.
Because existinq reflector structures are manufactured into one integrated whole, a decision cannot be made in the field to retrofit only part of an existing light fixture. Although light fixtures typically have a uniform design within any one general work area, frequently there is a variation in light fixture construction from one work area to another; therefore, a different retrofitting reflector is required for each differing work area. These reflectors are expensive to manufacture because they are fabricated from steel alloys. Further, they are costly to install because the typical electric drill and screws used to affix insert reflectors to a fixture involve a substantial labor and materials cost. And once screwed into place, the reflectors require a significant amount of labor time to be removed from the light fixtures if that is desired.
The type of reflector useful for one work area is often not efficient for a differing work area, even if the light fixtures have the same geometry in all work areas. For example, a hallway or stairwell presents a different lightinq situation than that found in an office space. In a hallway, it is preferable to direct a large percentage of the light to illuminate most brightly the hallway width at the floor. In contrast, in an office area it is preferable to spread light evenly throughout the area so the lighting level is constant throughout the work area.
These are only a few of the problems which have not been adequately resolved by previous approaches. For this reason it became necessary to devise the invention disclosed and claimed herein.